The preparation of reaction injection molded (RIM) elastomers such as non-cellular, rigid polyisocyanurate products is known and has become popular for the preparation of automobile body parts and other applications. Generally, the commercial RIM machines are of the two stream variety to prepare the reacted products, however three, four or more may be employed. The preparation of polyisocyanurate resins using a wide variety of trimerization catalysts is also known.
Rigid non-cellular polyurethane compositions from polyether polyols, isocyanates and organic carbonates are known using various modifiers and catalysts. The preparation of laminated composites are also well known and the laminates may contain such materials as metal, wood or other cellulosic material, plastic, glass, or ceramics. These resins may also be filled with fibers of these materials to add structural strength.
These reinforced resin components, also called structural RIM or SRIM, are also used in the automotive industry as substances to replace metal. ARSET.RTM. HI2801 and ARSET HT3500 resins are used to give polymers with high elongation, according to U. E. Younes, "Resins Resist Impact: Versatile SRIM Composites," Urethanes Technology, June/July 1990, pp. 20-23. RIM compositions using these resins which contain a soluble adduct of a tertiary amine and a cyclic alkylene carbonate as a catalyst are described in U.S. Pat. Nos. 4,709,002; 4,731,427; 4,757,123; 4,800,058; 4,879,164; and 4,886,700, incorporated by reference.
Polyurethane foams, as contrasted with RIM plastics, are known to bum readily and considerable effort has been devoted to reducing the flammability of the foams. One technique by which this may be done is through the use of additives to the foam that retard its flammability or help to extinguish the burning foam, should it ignite. Known flame retardant additives include 2,3-dibromo-1,4-butenediol; tris(2-chloroethyl)-phosphate and triethylphosphate, for example. However, a disadvantage of using the phosphate-containing additives is that often relatively large quantities of the expensive materials must be used, higher than about 1%. Additionally, phosphorus flame retardants can create a plasticizing effect which causes the polyurethane foam to be reduced in hardness, lower in compressive strength and increased in density so that the foam is detrimentally affected. These conventional flame retardants are also somewhat volatile and may evaporate out of the polyurethane foam over time, thus decreasing the available fire retardancy. Finally, there are indications that these materials may be corrosive to certain metals on which the foams are applied.
Considerable research has been conducted on flame retardant additives for polyurethane foams. For example, U.S. Pat. No. 4,221,875 describes flame resistant and non-corrosive polyurethane foams made by foaming a raw material mixture comprising a polyhydroxyl compound, polyisocyanate, blowing agent, etc., to be carried out in the presence of melamine powder added thereto as a novel flame retardant. See also UK Patent Application GB 2,177,405A which relates to flame retardant polyurethane foams prepared by reacting a polyoxyalkylene polyether polyol with an organic polyisocyanate and a blowing agent in a process where melamine is incorporated as the sole flame retardant compound. The amount of melamine ranges from 10 wt. % to 55 wt. % of the total composition. UK Patent Application GB 2,177,406A is similar to UK Patent Application 2,177,405A, except that another flame retardant is also used in combination with the melamine, where the other flame retardant may include tris(.beta.-chloroethyl)phosphate, pentabromodiphenyl oxide, tris(2,3-dibromopropyl)phosphate and tris(.beta.-chloropropyl )phosphate.
It is further well known to use chlorinated polyvinyl chloride in polyurethane compositions. Studies of the miscibility of blends of these systems are reported in D. Garcia, "Blends of a Chlorinated Poly(Vinyl Chloride) (CPVC) with a Polyurethane," Polymer Preparations, Vol. 27, No. 1, 1986, pp. 259060; D. Garcia, "Blends of a Chlorinated Poly(vinyl Chloride) with a Polyurethane," Journal of Polymer Science, Vol. 24, 1986, (pp. 1577-1586); and D. Garcia, "Blends of a Chlorinated Poly(vinyl) Chloride) (CPVC) with a Polyurethane," Polymer Preparations, Vol. 38, No. 1, 1987, pp. 120-1. It is noted that since these are miscibility studies, the proportion of chlorinated polyvinyl chloride to urethane is very high, sometimes over 40%.
Chlorinated polyvinyl chloride is also known to be used in polyurethane compositions to affect the viscosity. In Chemical Abstracts 106:(6):3471 g (1986), the viscosity of polypropylene glycol-TDI-trimethylolpropane copolymer and CPVC coating systems containing diluent plasticizers and polyols depended on the chemical nature of the diluents and on the content of the CPVC modifier. The incorporation of greater than 15% CPVC into a polyurethane film-forming composition comprising a copolymer of THF, propylene oxide, trimethylolpropane and TDI decreased (1) the curing time from 12 to 6-9 hours, (2) the gel-fraction content from 97 to 77-84%, (3) the relative hardness from 0.51 to 0.42-0.45, (4) the impact strength by approximately 5-20.times.10.sup.-2 kg-m, and (5) elasticity as well, but increased (1) the wear by approximately 58-90.times.10.sup.-5 kg/m.sup.2 -m, (2) the tensile strength, and (3) the resistance of the composition to the action of 20% aq. HNO.sub. 3, NaOH and water, according to Chemical Abstracts 95(22):188122e (1980). The recitation in Chemical Abstracts 92(26):216307c(1980) may also be of interest. The abstract describes a composition of 100 pans NCO-terminated polyurethane and 10-50 pans 20-40% CPVC solution in ethyl acetate which additionally contains 5-20 pans polyisocyanate and 1-10 pans ethoxylated alkylphenol for improved shelf life and for increased strength of the adhesive bond.
A known material for improving flammability in plastics is antimony trioxide (Sb.sub.2 O.sub.3).
"The most useful material imparting flame retardance to plastics is antimony trioxide. It must be used with a source of available chlorine to be effective; it is presumed that antimony oxychloride is the active flame-retarding agent." F. W. Billmeyer, Jr., Textbook of Polymer Science, Wiley/Interscience, New York, 1971, p. 502 referring to J. A. Holderreid, "Flame retardants," p. 274, 276, 288, 290 in Sidney Gross, ed., Modern Plastics Encyclopedia 1969-1970, McGraw-Hill, New York, Vol 46, No. 10A, October, 1969.
Antimony pentoxide, Sb.sub.2 O.sub.5, is also known as a time retardant for textiles. See Irving Sax, et al., Hawley's Condensed Chemical Dictionary, Eleventh Edition, Van Nostrand Reinhold, New York, 1987, p. 91.
Also of interest is U.S. Pat. No. 4,711,941, which relates to a moldable composition having a novel random bromostyrene-containing copolymer, a thermoplastic resin, preferably a polycarbonate, and a flame-retardant synergist. The list of suitable synergists includes antimony trioxide, antimony pentoxide, arsenic trioxide, arsenic pentoxide, zinc sulfate, zinc oxide, zinc borate, bismuth oxide, molybdenum oxide, tungsten oxide, stannous oxide, and their mixtures, with antimony trioxide being the preferred synergist.
It will be appreciated that, like many additives because a flame retardant shows promise with respect to one plastic, e.g. polyurethane flexible foams or molded polycarbonate copolymers, that one skilled in the art would not know in advance that the same additive would work in a different plastic, e.g. polyisocyanurate RIM, SRIM or reinforced RIM (RRIM).
Now flammability of RIM and SRIM materials is also an important issue, and improvements in this area are always sought. While additives might be useful in this regard, little is known of useful fire retardant additives for RIM materials.